The present technology relates to a display, such as an organic EL display, including an organic layer formed by a printing method, a method of manufacturing the same, and an electronic unit.
In recent years, methods of forming a light-emitting layer (an organic layer) of an organic EL (Electroluminescence) display device by a printing method have been proposed (for example, refer to Japanese Unexamined Patent Application Publication Nos. 2007-95514, 2009-238709, and 2010-247394). The printing method holds promise, since, compared to a vacuum deposition method, process cost is lower and upsizing of displays is easier.
The printing method is broadly classified into a non-contact printing method and a contact printing method. Examples of the non-contact printing method include an ink-jet printing method and a nozzle printing method. These methods are specifically suitable for manufacturing of large-screen displays, and are superior in material use efficiency. However, there are issues such as an increase in cost since a bank for determining an ink coating position is necessary, and a nonuniform film thickness distribution in a device pixel caused by the spread of an ink to the bank.
On the other hand, examples of the contact printing method include a flexographic printing method, a gravure offset printing method, and a reverse offset printing method. In the flexographic printing method, a film is formed on a substrate with good film thickness accuracy, and operation time for a printing step is short; therefore, upsizing of a printing machine is possible. However, the flexographic printing method has low plate accuracy, and it is thus difficult for the flexiographic printing method to cope with higher-definition displays or larger-screen displays. The gravure offset printing method has high plate accuracy, and is thus capable of coping with higher-definition displays or larger-screen displays; however, a film thickness distribution in a pattern forms a mountain-like shape, thereby causing nonuniform light emission luminance in pixels.
The reverse offset printing method is a method of uniformly forming a film of an ink on a blanket, and then pressing the film to a plate to remove a non-printing portion of the film, and transferring a pattern formed of the film remaining on the blanket to an object where the pattern is to be printed. In this method, a film with a uniform film thickness is formed, and high-definition patterning is performed; therefore, this method is expected to be applied to a field called printed electronics. More specifically, applications of this method to not only organic layers of organic EL devices, but also wiring/insulating patterns of printed circuit boards, resists in photolithography operation, color filters for display, and organic layers of organic TFTs (Thin Film Transistors) have been studied.